Polymorphous light eruption (PMLE) is the most common form of sun allergy. The condition is more commonly seen in women.

The symptoms of PMLE include:

• Itchy, burning rash on sun-exposed portions of the neck, chest, arms and lower legs
  
  
• Periods of chills, headache, nausea and feeling ill
  
  
• Red, flat or raised areas, fluid-filled blisters or tiny areas of bleeding under the skin

The itchy rash associated with PMLE appears on sun-exposed skin within the first two hours of sun exposure. The rash can take many forms, though its appearance is usually consistent during subsequent appearances in the same individual. PMLE symptoms usually first begin during early adulthood, but can appear at any age. Symptoms appear during the early spring, and gradually decrease as the skin becomes less sensitive to sunlight. Also known as hardening, this type of desensitization usually lasts through the end of summer. The PMLE rash may disappear entirely during the summer, and then return at full intensity the following spring. Some patients experience temporary remissions.

PMLE typically appears on limited areas at first. However, it often becomes more extensive during subsequent summers. PMLE-related lesions usually heal without scarring.

Actinic prurigo is the hereditary form of PMLE that occurs among those of American Indian background of North, South and Central America. The symptoms are more intense than those of PMLE and often first appear during childhood. Several generations of the same family may have a history of this skin condition. Actinic prurigo does not improve with time.

The symptoms of actinic prurigo are the same as PMLE but are concentrated on the face, especially around the lips. Symptoms are sometimes located in the eye membranes (conjunctiva) causing brown spots and extreme sensitivity to light. The rash will usually disappear within two to three days if sun exposure is avoided.

Long-term protection from sunlight is necessary to avoid worsening both conditions. However, many people with PMLE improve significantly within seven years of first displaying symptoms.